1. Field of the Invention
The present invention relates to a display device and a method for driving the same, and more particularly, to a display device and a method for driving the same that can uniformly maintain a degradation deviation of a whole display panel in upper, lower, left, and right directions in a self-luminescent display device.
2. Background of the Related Art
Generally, a display device has a degradation deviation on a display panel by driving the display panel. Recently, self-luminescent display devices, such as a cathode ray tube (CRT), a field emission display (FED), a plasma display panel (PDP), and an electroluminescence (EL), are used as display devices. Since such self-luminescent display devices have a variable screen in view of a graphic screen, certain pixels of a panel are not continuously maintained in turn-on or turn-off state.
However, in a text screen, when the text screen is continuously displayed, some of pixels constituting the text screen can continuously be maintained in turn-on state while other pixels can continuously be maintained in turn-off state.
Therefore, a great difference exists between luminance of pixels continuously maintained in turn-on state and luminance of pixels continuously maintained in turn-off state. In other words, the pixels continuously maintained in turn-on state have a short life due to degradation while the pixels continuously maintained in turn-off state relatively have a long life.
The pixels having different lives deteriorate picture quality of the display device.
To solve such a problem, there is provided a method for prolonging a life of a display panel of a display device by applying an inverse voltage to the display panel. However, this method is made without any noticeable result.
FIG. 1 is a diagram showing a display of a general text type.
Luminance according to lives of pixels continuously maintained in turn-off state in FIG. 1 is shown in an upper graph of FIG. 2. As shown in FIG. 2, it is noted that luminance of pixels continuously maintained in turn-on state according to their operation time is remarkably deteriorated as compared with the pixels continuously maintained in turn-off state.
Meanwhile, the pixels continuously maintained in turn-off state have lower luminance than the pixels continuously maintained in turn-on state. Luminance of pixels continuously maintained in turn-off state according to their operation time is shown in a lower graph of FIG. 2.
In other words, in the pixels continuously maintained in turn-on state, charges continuously move within them. Accordingly, as shown in the lower graph of FIG. 2, the pixels continuously maintained in turn-on state have rapidly deteriorated luminance according to life as compared with the pixels continuously maintained in turn-off state. Further, the pixels continuously maintained in turn-on state have a shorter life than the pixels continuously maintained in turn-off state.
Consequently, the life difference generates luminance difference between the pixels and deteriorates picture quality of the display device.
In other words, if the display device displays a text screen, once the pixels are set up in turn-on or turn-off state, they continuously remain as they are. In this case, luminance difference exists between the turned on pixels and the turned off pixels, thereby remarkably deteriorating picture quality.